In advanced metal oxide semiconductor (MOS) devices it is desirable to provide a gate electrode and interconnect with low electrical resistance. This is essential when the MOS device is a portion of a high density integrated circuit. Generally, a high density integrated circuit is a circuit having interconnect lines which are less than about two micrometers wide, although it will be understood by those skilled in the art that the greater the overall length of the interconnect, which essentially connects in series chains of components in the IC, the greater the need for a low resistance material to form the gate electrodes and interconnects.
At the present time polycrystalline silicon (polysilicon) is used for both gate electrode and interconnect on MOS devices because of its compatibility with high temperature processing which is required subsequent to deposition of the electrode and interconnect. Polysilicon is compatible with subsequent processes and, like single crystal silicon, can be controllably oxidized subsequent to deposition without catastrophic oxidative destruction. Any substitute for the polysilicon gate and interconnect must likewise be compatible with the manufacturing processes, i.e., it must resist oxidation (i.e. be controllably oxidizable), resist the aqueous chemicals and plasmas used in cleaning and etching, and must exhibit the same, or better, conductivity and contact resistance characteristics as polysilicon, especially the contact resistance to doped silicon.
Oxidation resistance is the most difficult of these characteristic to obtain. Molybdenum and tungsten, for example, oxidize to form a volatile oxide which evaporates at high temperatures so that in less than one minute at the high temperature a complete layer of deposited material will disappear. This oxidation can be slowed down by forming a silicide compound. Additionally, many of the known metal disilicides, MeSi.sub.2, (i.e., where Me represents molybdenum, tungsten, titanium, etc.) are ten times more conductive than n+ silicon. The refractory metals and silicides, however, are generally characterized by poor contact resistance, especially to monocrystalline silicon, and by processing difficulties.